2600:
2862:
2566:
2826:
2850:
49:
2802:
2838:
2814:
636:
10 mi). Bessel added that light takes 10.3 years to traverse this distance. He recognized that his readers would enjoy the mental picture of the approximate transit time for light, but he refrained from using the light-year as a unit. He may have resisted expressing distances in light-years
2275:
Tuomi, Mikko; Jones, Hugh R. A.; Jenkins, James S.; Tinney, Chris G.; Butler, R. Paul; Vogt, Steve S.; Barnes, John R.; Wittenmyer, Robert A.; O'Toole, Simon; Horner, Jonathan; Bailey, Jeremy; Carter, Brad D.; Wright, Duncan J.; Salter, Graeme S.; Pinfield, David (March 2013).
2556:
2554:
666:
A contemporary German popular astronomical book also noticed that light-year is an odd name. In 1868 an
English journal labelled the light-year as a unit used by the Germans.
2336:
Eisenhauer, F.; Schdel, R.; Genzel, R.; Ott, T.; Tecza, M.; Abuter, R.; Eckart, A.; Alexander, T. (2003), "A Geometric
Determination of the Distance to the Galactic Center",
469:(not the Julian year) and a measured (not defined) speed of light were included in the IAU (1964) System of Astronomical Constants, used from 1968 to 1983. The product of
2634:
624:, equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's
2555:
355:, used since 1984. From this, the following conversions can be derived. The abbreviation used by the IAU for light-year is "ly",. International standards like
1704:
1894:
2428:
697:. Galaxies themselves span from a few thousand to a few hundred thousand light-years in diameter, and are separated from neighbouring galaxies and
2627:
1788:
1406:. However, smaller units of length can similarly be formed usefully by multiplying units of time by the speed of light. For example, the
2892:
2620:
1045:, an extrasolar candidate for a habitable planet. 6.6 times as massive as the earth, it is in the middle of the habitable zone of star
670:
called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations.
2427:
Fujisawa, K.; Inoue, M.; Kobayashi, H.; Murata, Y.; Wajima, K.; Kameno, S.; Edwards, P. G.; Hirabayashi, H.; Morimoto, M. (2000),
1367:
from the Earth to the edge of the visible universe is about 45.7 billion light-years in any direction; this is the comoving
1321:
637:
because it would reduce the accuracy of his parallax data due to multiplying with the uncertain parameter of the speed of light.
604:
The light-year unit appeared a few years after the first successful measurement of the distance to a star other than the Sun, by
866:, was about 18 light-hours (130 au,19.4 billion km, 12.1 billion mi) away from the Earth as of October 2014. It will take about
359:(now superseded) have used "l.y." and localized abbreviations are frequent, such as "al" in French, Spanish, and Italian (from
2472:
Junor, W.; Biretta, J. A. (1994), "The Inner Light-Month of the M87 Jet", in Zensus, J. Anton; Kellermann; Kenneth I. (eds.),
2520:
2025:
1995:
1958:
1932:
1859:
1833:
1756:
1442:
publications. The light-month, roughly one-twelfth of a light-year, is also used occasionally for approximate measures. The
522:
reference work, which was updated in 2000, including the IAU (1976) value cited above (truncated to 10 significant digits).
2131:
1295:
lies at a distance of somewhere between 150 and 250 million light-years (the latter being the most recent estimate).
2474:
Compact
Extragalactic Radio Sources, Proceedings of the NRAO workshop held at Socorro, New Mexico, February 11–12, 1994
2052:
1462:
1384:
1771:
2604:
2493:
321:
270:
1681:
297:
2897:
2076:
67:
2191:
2099:
648:). It was not yet considered to be a fundamental constant of nature, and the propagation of light through the
1701:
1515:
839:
at a distance of 4.7 billion kilometres, and the communication takes 4 hours 25 minutes to reach Earth.
172:
124:
2774:
2658:
1478:
204:
72:
1900:
1972:
1380:
31:
2458:
2792:
698:
659:. Ule explained the oddity of a distance unit name ending in "year" by comparing it to a walking hour (
656:
514:
in the speed of light) found in several modern sources was probably derived from an old source such as
17:
2590:
910:
as of
October 2018, nearly 20 light-hours (144 au, 21.6 billion km, 13.4 billion mi) from the Earth.
677:, light-years are also popularly used to gauge the expanses of interstellar and intergalactic space.
1659:
787:
to the Earth). It takes approximately 499 seconds (8.32 minutes) for light to travel this distance.
2902:
2887:
748:'s surface takes 1.2–1.3 seconds to travel the distance to the Earth's surface (travelling roughly
640:
The speed of light was not yet precisely known in 1838; the estimate of its value changed in 1849 (
2217:
1247:), at about 3 million light-years away, is the most distant object visible to the naked eye.
325:
278:
1438:
of a light-year. Units such as the light-minute, light-hour and light-day are sometimes used in
2769:
1473:
1317:
1193:
2232:
2115:
2015:
1985:
1948:
1794:
281:(365.25 days). Because it includes the word "year", the term is sometimes misinterpreted as a
2510:
2278:"Signals embedded in the radial velocity noise: periodic variations in the τ Ceti velocities"
1922:
617:
352:
262:
2391:; Madsen, J. B.; Barnes, J.; Ericksen, B. F. (2000), "The Distance to the Galactic Center",
2306:
1849:
1746:
2586:
2477:
2440:
2400:
2355:
2302:
1713:
1629:
2249:
628:
of 0.314 arcseconds, showed the distance to the star to be 660,000 astronomical units (9.9
8:
2854:
2779:
2671:
2571:
1376:
1372:
982:
886:
881:, 61 200 km/h) relative to the Sun. On 12 September 2013, NASA scientists announced that
649:
266:
2481:
2444:
2404:
2359:
2039:
1633:
931:
is approximately two light-years in diameter. Its inner boundary is speculated to be at
2842:
2830:
2388:
2371:
2345:
2318:
2292:
1443:
543:
found in some modern sources is the product of a mean
Gregorian year (365.2425 days or
511:
329:
269:: 9.4607304725808 × 10 km), which is approximately 5.88 trillion mi. As defined by the
2277:
2716:
2516:
2021:
1991:
1954:
1928:
1855:
1829:
1752:
1468:
1403:
1364:
1240:
780:
621:
441:
221:
2612:
2375:
1025:
2806:
2448:
2408:
2363:
2322:
2310:
1875:
1637:
1313:
1222:
1004:
706:
694:
667:
641:
605:
579:, is the product of the J1900.0 mean tropical year and the defined speed of light.
488:
2314:
645:
1708:
1439:
1292:
1136:
655:
The light-year unit appeared in 1851 in a German popular astronomical article by
301:
2152:
2882:
2866:
2643:
2169:
1594:
1559:
1410:, useful in astronomy, telecommunications and relativistic physics, is exactly
1262:
1244:
816:
and transmits images from its surface, 1.2 billion kilometres from Earth.
526:
337:
292:
is most often used when expressing distances to stars and other distances on a
274:
258:
168:
1028:
than the Sun, it outshines more luminous stars due to its relative proximity.
620:. The largest unit for expressing distances across space at that time was the
2876:
2453:
1266:
802:
470:
466:
333:
120:
2426:
1809:
2818:
2697:
2691:
2506:
2476:, Green Bank, WV: National Radio Astronomy Observatory (NRAO), p. 97,
1617:
1407:
1084:
970:
890:
889:
of space on 25 August 2012, becoming the first manmade object to leave the
831:
809:
515:
282:
2065:
Bessel's statement that light employs 10.3 years to traverse the distance.
1453:; the term "light-foot" is sometimes used as an informal measure of time.
1446:
specifies the light month more precisely as 30 days of light travel time.
1024:, the brightest star of the night sky. Twice as massive and 25 times more
873:
years to reach one light-year at its current speed of about 17 km/s (
2350:
2081:
Deutsches Museum: Zeitschrift für
Literatur, Kunst und Öffentliches Leben
1402:
tend to be small fractions of a light-year, and are usually expressed in
1399:
1324:) has been measured to be approximately one billion light-years distant.
966:
857:
2599:
2574:
was created from a revision of this article dated 27 June 2005
1083:, second in brightness in the terrestrial sky only to Sirius, a type A9
53:
Map showing stars and star systems lying within 12.5 light-years of the
2752:
2746:
2740:
2011:
1450:
1197:
1114:
1063:
1042:
928:
690:
613:
2861:
1687:
2722:
2710:
2647:
1641:
1165:
1140:
862:
582:
Abbreviations used for light-years and multiples of light-years are:
413:
356:
305:
154:
2117:
The
Student and Intellectual Observer of Science, Literature and Art
1735:
IEEE/ASTM SI 10-2010, American
National Standard for Metric Practice
2413:
2367:
2193:
NASA Spacecraft
Embarks on Historic Journey Into Interstellar Space
1110:
1046:
625:
609:
2297:
2057:
London and
Edinburgh Philosophical Magazine and Journal of Science
1751:, Mill Valley, California: University Science Books, p. 656,
2515:. Princeton, New Jersey: Princeton University Press. p. 22.
1080:
474:
1200:
of the Sun, has an apparent magnitude 12.77, just brighter than
595:"Gly" or "Glyr" for a gigalight-year (1,000,000,000 light-years)
2734:
2120:. Vol. 1. London: Groombridge and Sons. 1868. p. 240.
1368:
1346:
1342:
1338:
1201:
1189:
1021:
813:
714:
702:
674:
455:
309:
293:
229:
48:
961:
Approximate maximum distance at which an object can orbit the
689:
in the same general area, such as those belonging to the same
30:
This article is about the unit of length. For other uses, see
1196:, the most luminous star known at 8.7 million times the
836:
142:
2387:
1592:
2429:"Large Angle Bending of the Light-Month Jet in Centaurus A"
2213:
1000:
745:
686:
190:
2813:
1560:"The Universe within 12.5 Light Years – The Nearest stars"
304:
publications. The unit most commonly used in professional
2335:
2250:"Tau Ceti's planets nearest around single, Sun-like star"
1890:
1854:(fourth ed.), New York: Springer-Valeg, p. 12,
962:
784:
701:
by millions of light-years. Distances to objects such as
685:
Distances expressed in light-years include those between
589:"kly" or "klyr" for a kilolight-year (1,000 light-years)
54:
2494:
Light-Travel Time and Distance by the Hayden Planetarium
2237:
Encyclopedia of Astrobiology, Astronomy, and Spaceflight
2471:
2393:
Publications of the Astronomical Society of the Pacific
2274:
1066:, a red-dwarf star with several detectable exoplanets.
1726:
ISO 80000-3:2006 Quantities and Units – Space and Time
1596:
Measuring the Universe: The IAU and Astronomical Units
1465:(examples of distances on the order of one light-year)
2790:
2642:
2132:"Stellar movements and the structure of the universe"
1744:
1349:. 3C 273 is about 2.4 billion light-years away.
2512:
It's About Time: Understanding Einstein's Relativity
1618:"Milliarcsecond structure of BL Lac during outburst"
1616:
Mutel, R. L.; Aller, H. D.; Phillips, R. B. (1981).
1225:
is approximately 2.5 million light-years away.
673:
Although modern astronomers often prefer to use the
525:Other high-precision values are not derived from a
1748:Explanatory Supplement to the Astronomical Almanac
1615:
981:). Beyond this is the deep ex-solar gravitational
592:"Mly" for a megalight-year (1,000,000 light-years)
2433:Publications of the Astronomical Society of Japan
2101:Populäre Himmelskunde u. astronomische Geographie
265:and is equal to exactly 9,460,730,472,580.8 km (
2874:
1828:(third ed.), London: Athlone, p. 16,
1345:, of apparent magnitude 12.9, just dimmer than
1953:(fifth ed.), W. H. Freeman, p. 365,
1920:
1807:
2628:
1847:
1657:
1269:, is about 59 million light-years away.
612:, and he used a 160-millimetre (6.2 in)
328:(365.25 days, as opposed to the 365.2425-day
2505:
351:). Both of these values are included in the
324:(IAU), the light-year is the product of the
1823:
1497:One Julian year is exactly 365.25 days (or
353:IAU (1976) System of Astronomical Constants
2635:
2621:
2097:
2020:(fourth ed.), Springer, p. 620,
1738:
1449:Light travels approximately one foot in a
2452:
2412:
2349:
2296:
2219:Cosmic Distance Scales – The Nearest Star
1924:Applied dimensional analysis and modeling
709:run up into the billions of light-years.
273:(IAU), a light-year is the distance that
2582:, and does not reflect subsequent edits.
2565:
2009:
1873:
1786:
1588:
1586:
1584:
1582:
1580:
1983:
1977:
27:Distance that light travels in one year
14:
2875:
2053:"On the parallax of the star 61 Cygni"
2050:
1946:
1940:
1653:
1651:
381:
312:(symbol: pc, about 3.26 light-years).
2616:
1927:, New York: McGraw-Hill, p. 60,
1577:
2003:
1683:IAU Recommendations concerning Units
370:respectively), "Lj" in German (from
2098:Diesterweg, Adolph Wilhelm (1855).
2074:
1745:P. Kenneth Seidelmann, ed. (1992),
1648:
1398:Distances between objects within a
24:
2552:
1950:Discovering the Essential Universe
1593:International Astronomical Union,
1093:times more luminous than the Sun.
1007:, is about 4.24 light-years away.
554:) and the defined speed of light (
25:
2914:
2893:Units of measurement in astronomy
2533:
939:≈ 0.8 ly, with its outer edge at
2860:
2848:
2836:
2824:
2812:
2800:
2598:
2564:
2212:
1889:
1851:Allen's Astrophysical Quantities
1527:The speed of light is precisely
1393:
713:List of orders of magnitude for
680:
322:International Astronomical Union
271:International Astronomical Union
47:
2499:
2487:
2465:
2420:
2381:
2329:
2268:
2242:
2233:"Proxima Centauri (Gliese 551)"
2225:
2206:
2184:
2162:
2145:
2124:
2108:
2091:
2068:
2044:
2033:
1966:
1914:
1883:
1867:
1841:
1817:
1801:
1790:Table of astronomical constants
1780:
1764:
1729:
1702:Selected Astronomical Constants
336:that both approximate) and the
2077:"Was wir in den Sternen lesen"
1720:
1694:
1674:
1658:Bruce McClure (31 July 2018).
1609:
1552:
1521:
1491:
652:or space was still enigmatic.
315:
13:
1:
2603:The dictionary definition of
1545:
2775:Orders of magnitude (length)
2659:Astronomical system of units
2285:Astronomy & Astrophysics
1479:Orders of magnitude (length)
744:Reflected sunlight from the
7:
2315:10.1051/0004-6361/201220509
1848:Arthur N. Cox, ed. (2000),
1538:by definition of the metre.
1456:
1381:cosmic background radiation
1353:
1328:
1302:
1273:
1251:
1229:
1211:
1179:
1154:
1125:
1113:, the second-nearest known
1100:
1070:
1053:
1032:
1011:
989:
951:
917:
897:
846:
820:
791:
769:
734:
32:Light year (disambiguation)
10:
2919:
2051:Bessel, Friedrich (1839).
1990:, CRC Press, p. 445,
1660:"How far is a light-year?"
1564:www.atlasoftheuniverse.com
1508:based on a day of exactly
1387:for why this is possible.
1375:. This is larger than the
1341:, optically the brightest
599:
29:
2762:
2667:
2654:
2338:The Astrophysical Journal
2017:Encyclopedia of Distances
1316:(not to be confused with
1299:
1208:
1097:
914:
843:
766:
499:produced a light-year of
275:light travels in a vacuum
200:
164:
116:
112:
94:
86:
78:
66:
61:
46:
41:
1947:Comins, Neil F. (2013),
1826:Astrophysical Quantities
1484:
520:Astrophysical Quantities
491:and a speed of light of
245:, alternatively spelled
2307:2013A&A...551A..79T
2171:WHERE ARE THE VOYAGERS?
2157:IERS Conventions (2003)
1984:Hassani, Sadri (2010),
1921:Thomas Szirtes (1997),
783:(the distance from the
586:"ly" for one light-year
529:IAU system. A value of
2770:Cosmic distance ladder
2560:
2540:Listen to this article
2496:Accessed October 2010.
2454:10.1093/pasj/52.6.1021
2153:"Chapter 1, Table 1-1"
1987:From Atoms to Galaxies
1896:Astronomical Constants
1877:Astronomical Constants
1194:Large Magellanic Cloud
1003:(other than the Sun),
608:in 1838. The star was
510:(rounded to the seven
477:mean tropical year of
263:astronomical distances
2898:Concepts in astronomy
2559:
618:Joseph von Fraunhofer
424:trillion kilometres (
332:or the 365.24219-day
296:scale, especially in
2591:More spoken articles
2010:Deza, Michel Marie;
1824:C. W. Allen (1973),
1808:Robert A. Braeunig,
1714:Astronomical Almanac
1175:light-years across.
382:1 light-year
2780:Conversion of units
2482:1994cers.conf...97J
2461:on 2 September 2009
2445:2000PASJ...52.1021F
2405:2000PASP..112..202M
2360:2003ApJ...597L.121E
1903:on 9 September 2007
1797:on 11 December 2008
1690:on 16 February 2007
1634:1981Natur.294..236M
1377:age of the universe
1373:observable universe
983:interstellar medium
887:interstellar medium
717:
267:Scientific notation
107:... is equal to ...
62:General information
2561:
2256:. 19 December 2012
2075:Ule, Otto (1851).
2040:Sanchez et al 2022
1707:2014-07-26 at the
1444:Hayden Planetarium
1404:astronomical units
1261:The nearest large
1150:light-years away.
1121:light-years away.
999:The nearest known
712:
565:). Another value,
512:significant digits
442:astronomical units
320:As defined by the
210:
205:astronomical units
202:
179:
166:
131:
118:
2788:
2787:
2717:Astronomical unit
2557:
2522:978-0-691-14127-5
2027:978-3-662-52843-3
1997:978-1-4398-0850-4
1960:978-1-4292-5519-6
1934:978-0-07-062811-3
1861:978-0-387-98746-0
1835:978-0-485-11150-7
1758:978-0-935702-68-2
1628:(5838): 236–238.
1469:Einstein protocol
1391:
1390:
1365:comoving distance
1241:Triangulum Galaxy
856:The most distant
781:astronomical unit
622:astronomical unit
489:ephemeris seconds
465:Before 1984, the
461:
460:
404:metres (exactly)
239:
238:
95:Conversions
16:(Redirected from
2910:
2865:
2864:
2853:
2852:
2851:
2841:
2840:
2839:
2829:
2828:
2827:
2817:
2816:
2805:
2804:
2803:
2796:
2637:
2630:
2623:
2614:
2613:
2602:
2581:
2579:
2568:
2567:
2558:
2548:
2546:
2541:
2527:
2526:
2503:
2497:
2491:
2485:
2484:
2469:
2463:
2462:
2457:, archived from
2456:
2424:
2418:
2417:
2416:
2385:
2379:
2378:
2353:
2351:astro-ph/0306220
2333:
2327:
2326:
2300:
2282:
2272:
2266:
2265:
2263:
2261:
2246:
2240:
2239:
2229:
2223:
2222:
2210:
2204:
2203:
2202:
2200:
2188:
2182:
2181:
2180:
2178:
2166:
2160:
2159:
2149:
2143:
2142:
2140:
2138:
2128:
2122:
2121:
2112:
2106:
2105:
2095:
2089:
2088:
2072:
2066:
2064:
2048:
2042:
2037:
2031:
2030:
2007:
2001:
2000:
1981:
1975:
1970:
1964:
1963:
1944:
1938:
1937:
1918:
1912:
1911:
1910:
1908:
1899:, archived from
1887:
1881:
1880:
1871:
1865:
1864:
1845:
1839:
1838:
1821:
1815:
1814:
1805:
1799:
1798:
1793:, archived from
1784:
1778:
1777:
1776:, Sierra College
1768:
1762:
1761:
1742:
1736:
1733:
1727:
1724:
1718:
1698:
1692:
1691:
1686:, archived from
1678:
1672:
1671:
1669:
1667:
1655:
1646:
1645:
1642:10.1038/294236a0
1613:
1607:
1606:
1605:
1603:
1590:
1575:
1574:
1572:
1570:
1556:
1539:
1537:
1535:
1532:
1525:
1519:
1514:
1513:
1507:
1505:
1502:
1495:
1437:
1436:
1435:
1434:
1431:
1424:
1419:
1418:
1415:
1379:dictated by the
1360:
1358:
1335:
1333:
1314:Sloan Great Wall
1309:
1307:
1288:
1286:
1280:
1278:
1258:
1256:
1236:
1234:
1223:Andromeda Galaxy
1218:
1216:
1186:
1184:
1174:
1173:
1161:
1159:
1149:
1148:
1132:
1130:
1120:
1107:
1105:
1092:
1091:
1077:
1075:
1060:
1058:
1039:
1037:
1018:
1016:
1005:Proxima Centauri
996:
994:
980:
978:
958:
956:
946:
944:
938:
936:
924:
922:
904:
902:
885:had entered the
880:
878:
872:
871:
853:
851:
827:
825:
798:
796:
776:
774:
761:
760:
754:
753:
741:
739:
718:
711:
707:Sloan Great Wall
695:globular cluster
635:
631:
606:Friedrich Bessel
578:
576:
573:
570:
564:
562:
559:
553:
551:
548:
542:
540:
537:
534:
509:
507:
504:
498:
496:
487:
485:
482:
454:
453:
440:
438:
428:trillion miles)
427:
423:
412:
403:
402:
399:
396:
393:
390:
379:
378:
350:
348:
345:
261:used to express
232:
224:
219:
211:
203:
193:
188:
180:
167:
157:
152:
145:
140:
132:
119:
51:
39:
38:
21:
2918:
2917:
2913:
2912:
2911:
2909:
2908:
2907:
2903:1838 in science
2888:Units of length
2873:
2872:
2871:
2859:
2849:
2847:
2837:
2835:
2825:
2823:
2811:
2801:
2799:
2791:
2789:
2784:
2758:
2706:
2703:
2686:
2680:
2677:
2663:
2650:
2644:Units of length
2641:
2595:
2594:
2583:
2577:
2575:
2572:This audio file
2569:
2562:
2553:
2550:
2544:
2543:
2539:
2536:
2531:
2530:
2523:
2504:
2500:
2492:
2488:
2470:
2466:
2425:
2421:
2389:McNamara, D. H.
2386:
2382:
2334:
2330:
2280:
2273:
2269:
2259:
2257:
2248:
2247:
2243:
2231:
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2226:
2211:
2207:
2198:
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2189:
2185:
2176:
2174:
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2130:
2129:
2125:
2114:
2113:
2109:
2096:
2092:
2073:
2069:
2049:
2045:
2038:
2034:
2028:
2008:
2004:
1998:
1982:
1978:
1971:
1967:
1961:
1945:
1941:
1935:
1919:
1915:
1906:
1904:
1888:
1884:
1872:
1868:
1862:
1846:
1842:
1836:
1822:
1818:
1811:Basic Constants
1806:
1802:
1785:
1781:
1773:Basic Constants
1770:
1769:
1765:
1759:
1743:
1739:
1734:
1730:
1725:
1721:
1709:Wayback Machine
1699:
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1440:popular science
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1411:
1396:
1356:
1354:
1331:
1329:
1305:
1303:
1293:Great Attractor
1284:
1282:
1276:
1274:
1254:
1252:
1232:
1230:
1214:
1212:
1182:
1180:
1171:
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1146:
1144:
1128:
1126:
1118:
1103:
1101:
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1056:
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1035:
1033:
1014:
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992:
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976:
974:
954:
952:
942:
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934:
932:
920:
918:
900:
898:
876:
874:
869:
867:
849:
847:
823:
821:
794:
792:
772:
770:
758:
756:
751:
749:
737:
735:
699:galaxy clusters
683:
633:
632:10 km; 6.1
629:
602:
574:
571:
568:
566:
560:
557:
555:
549:
546:
544:
538:
535:
532:
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451:
449:
436:
434:
425:
421:
410:
400:
397:
394:
391:
388:
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346:
343:
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318:
302:popular science
235:
227:
217:
215:
209:
201:
196:
186:
184:
178:
165:
160:
150:
148:
138:
136:
130:
117:
73:astronomy units
57:
35:
28:
23:
22:
15:
12:
11:
5:
2916:
2906:
2905:
2900:
2895:
2890:
2885:
2870:
2869:
2857:
2845:
2833:
2821:
2809:
2786:
2785:
2783:
2782:
2777:
2772:
2767:
2763:
2760:
2759:
2757:
2756:
2750:
2744:
2738:
2732:
2726:
2720:
2714:
2708:
2704:
2701:
2695:
2689:
2684:
2678:
2675:
2668:
2665:
2664:
2662:
2661:
2655:
2652:
2651:
2640:
2639:
2632:
2625:
2617:
2611:
2610:
2584:
2570:
2563:
2551:
2538:
2537:
2535:
2534:External links
2532:
2529:
2528:
2521:
2498:
2486:
2464:
2439:(6): 1021–26,
2419:
2414:10.1086/316512
2380:
2368:10.1086/380188
2328:
2267:
2241:
2224:
2205:
2183:
2161:
2144:
2123:
2107:
2104:. p. 250.
2090:
2067:
2043:
2032:
2026:
2002:
1996:
1976:
1965:
1959:
1939:
1933:
1913:
1882:
1874:Nick Strobel,
1866:
1860:
1840:
1834:
1816:
1800:
1787:Marc Sauvage,
1779:
1763:
1757:
1737:
1728:
1719:
1693:
1673:
1647:
1608:
1576:
1550:
1549:
1547:
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1541:
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1520:
1489:
1488:
1486:
1483:
1482:
1481:
1476:
1471:
1466:
1458:
1455:
1395:
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1389:
1388:
1361:
1351:
1350:
1336:
1326:
1325:
1310:
1301:
1297:
1296:
1289:
1271:
1270:
1263:galaxy cluster
1259:
1249:
1248:
1237:
1227:
1226:
1219:
1210:
1206:
1205:
1187:
1177:
1176:
1162:
1152:
1151:
1133:
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1108:
1099:
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1019:
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1008:
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911:
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789:
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777:
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729:
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682:
679:
601:
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596:
593:
590:
587:
463:
462:
459:
458:
445:
444:
430:
429:
417:
416:
406:
405:
383:
361:année-lumière,
357:ISO 80000:2006
338:speed of light
330:Gregorian year
317:
314:
298:non-specialist
259:unit of length
237:
236:
234:
233:
225:
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207:
198:
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181:
176:
162:
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2669:
2666:
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2645:
2638:
2633:
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2626:
2624:
2619:
2618:
2615:
2609:at Wiktionary
2608:
2607:
2601:
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2596:
2592:
2588:
2573:
2524:
2518:
2514:
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2490:
2483:
2479:
2475:
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2460:
2455:
2450:
2446:
2442:
2438:
2434:
2430:
2423:
2415:
2410:
2406:
2402:
2398:
2394:
2390:
2384:
2377:
2373:
2369:
2365:
2361:
2357:
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2347:
2343:
2339:
2332:
2324:
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2294:
2290:
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2279:
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2255:
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2238:
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2221:
2220:
2215:
2209:
2195:
2194:
2187:
2173:
2172:
2165:
2158:
2154:
2148:
2133:
2127:
2119:
2118:
2111:
2103:
2102:
2094:
2086:
2082:
2078:
2071:
2062:
2058:
2054:
2047:
2041:
2036:
2029:
2023:
2019:
2018:
2013:
2006:
1999:
1993:
1989:
1988:
1980:
1974:
1973:Viollier 1994
1969:
1962:
1956:
1952:
1951:
1943:
1936:
1930:
1926:
1925:
1917:
1902:
1898:
1897:
1892:
1886:
1879:
1878:
1870:
1863:
1857:
1853:
1852:
1844:
1837:
1831:
1827:
1820:
1813:
1812:
1804:
1796:
1792:
1791:
1783:
1775:
1774:
1767:
1760:
1754:
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1749:
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1732:
1723:
1716:
1715:
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1677:
1661:
1654:
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1631:
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1598:
1597:
1589:
1587:
1585:
1583:
1581:
1565:
1561:
1555:
1551:
1524:
1517:
1494:
1490:
1480:
1477:
1475:
1474:Hubble length
1472:
1470:
1467:
1464:
1461:
1460:
1454:
1452:
1447:
1445:
1441:
1409:
1405:
1401:
1394:Related units
1386:
1382:
1378:
1374:
1370:
1366:
1362:
1352:
1348:
1344:
1340:
1337:
1327:
1323:
1319:
1315:
1311:
1298:
1294:
1290:
1272:
1268:
1267:Virgo Cluster
1264:
1260:
1250:
1246:
1242:
1238:
1228:
1224:
1220:
1207:
1203:
1199:
1195:
1191:
1188:
1178:
1167:
1163:
1153:
1142:
1138:
1134:
1124:
1116:
1112:
1109:
1096:
1086:
1082:
1079:
1069:
1065:
1062:
1052:
1048:
1044:
1041:
1031:
1027:
1023:
1020:
1010:
1006:
1002:
998:
988:
984:
972:
968:
964:
960:
950:
930:
926:
913:
909:
906:
896:
892:
888:
884:
865:
864:
859:
855:
842:
838:
834:
833:
829:
819:
815:
811:
807:
805:
800:
790:
786:
782:
778:
765:
762:kilometres).
747:
743:
731:
730:
726:
723:
720:
719:
716:
710:
708:
704:
700:
696:
692:
688:
681:Usage of term
678:
676:
671:
669:
664:
662:
658:
653:
651:
647:
643:
638:
627:
623:
619:
615:
611:
607:
594:
591:
588:
585:
584:
583:
580:
528:
523:
521:
517:
513:
490:
476:
472:
471:Simon Newcomb
468:
467:tropical year
457:
447:
446:
443:
432:
431:
419:
418:
415:
408:
407:
384:
380:
377:
376:
375:
373:
369:
365:
362:
358:
354:
339:
335:
334:Tropical year
331:
327:
323:
313:
311:
307:
303:
300:contexts and
299:
295:
291:
286:
284:
280:
276:
272:
268:
264:
260:
256:
252:
248:
244:
231:
226:
223:
214:
213:
208:
206:
199:
192:
183:
182:
177:
174:
170:
163:
156:
147:
144:
135:
134:
129:
126:
122:
115:
111:
108:
105:
103:
99:
98:
93:
89:
85:
81:
77:
74:
71:
69:
65:
60:
56:
50:
45:
40:
37:
33:
19:
2855:Solar System
2728:
2698:Solar radius
2692:Light-second
2682:
2672:Earth radius
2605:
2511:
2507:David Mermin
2501:
2489:
2473:
2467:
2459:the original
2436:
2432:
2422:
2399:(768): 202,
2396:
2392:
2383:
2341:
2337:
2331:
2288:
2284:
2270:
2258:. Retrieved
2253:
2244:
2236:
2227:
2218:
2208:
2197:, retrieved
2192:
2186:
2175:, retrieved
2170:
2164:
2156:
2147:
2135:. Retrieved
2126:
2116:
2110:
2100:
2093:
2084:
2080:
2070:
2060:
2056:
2046:
2035:
2016:
2005:
1986:
1979:
1968:
1949:
1942:
1923:
1916:
1905:, retrieved
1901:the original
1895:
1885:
1876:
1869:
1850:
1843:
1825:
1819:
1810:
1803:
1795:the original
1789:
1782:
1772:
1766:
1747:
1740:
1731:
1722:
1712:
1696:
1688:the original
1682:
1676:
1664:. Retrieved
1625:
1621:
1611:
1600:, retrieved
1595:
1567:. Retrieved
1563:
1554:
1523:
1493:
1448:
1408:light-second
1397:
1085:bright giant
971:Roche sphere
907:
891:Solar System
882:
861:
832:New Horizons
830:
803:
684:
672:
665:
660:
654:
644:) and 1862 (
639:
616:designed by
603:
581:
524:
519:
497:.5 km/s
464:
371:
367:
363:
360:
319:
289:
287:
283:unit of time
254:
250:
246:
242:
240:
228:0.3066
106:
101:
79:Unit of
36:
2843:Outer space
2831:Spaceflight
2344:(2): L121,
2012:Deza, Elena
1602:10 November
1463:1 petametre
1400:star system
1117:, is about
967:Hill sphere
858:space probe
835:encounters
721:Scale (ly)
516:C. W. Allen
326:Julian year
316:Definitions
279:Julian year
68:Unit system
2877:Categories
2753:gigaparsec
2747:megaparsec
2741:kiloparsec
2729:light-year
2606:light-year
2587:Audio help
2578:2005-06-27
2260:1 November
2199:14 October
2177:14 October
2137:1 November
2087:: 721–738.
1907:5 November
1666:15 October
1662:. EarthSky
1546:References
1451:nanosecond
1420:metres or
1359:10 ly
1334:10 ly
1322:Her–CrB GW
1318:Great Wall
1308:10 ly
1287:10 ly
1257:10 ly
1235:10 ly
1217:10 ly
1198:luminosity
1185:10 ly
1160:10 ly
1131:10 ly
1115:black hole
1106:10 ly
1076:10 ly
1064:Gliese 581
1059:10 ly
1043:Tau Ceti e
1038:10 ly
1017:10 ly
995:10 ly
957:10 ly
947:≈ 1.6 ly.
929:Oort cloud
923:10 ly
903:10 ly
852:10 ly
826:10 ly
797:10 ly
775:10 ly
740:10 ly
691:spiral arm
614:heliometre
414:petametres
368:anno luce,
290:light-year
247:light year
243:light-year
100:1 ly
42:Light-year
18:Light year
2807:Astronomy
2723:terametre
2711:gigametre
2648:Astronomy
2298:1212.4277
1536: m/s
1192:, in the
1168:is about
1166:Milky Way
1143:is about
1141:Milky Way
908:Voyager 1
883:Voyager 1
879: mph
863:Voyager 1
808:lands on
668:Eddington
661:Wegstunde
577:10 m
563: m/s
541:10 m
508:10 m
372:Lichtjahr
349: m/s
306:astronomy
2766:See also
2705:☉
2646:used in
2589: ·
2509:(2009).
2376:16425333
2254:BBC News
2063:: 68–72.
2014:(2016),
1705:Archived
1518:seconds)
1457:See also
1111:A0620-00
1047:Tau Ceti
1026:luminous
979: au
945: au
937: au
705:and the
657:Otto Ule
646:Foucault
626:parallax
610:61 Cygni
527:coherent
518:'s 1973
374:), etc.
294:galactic
257:), is a
189:10
169:imperial
141:10
2867:Science
2793:Portals
2576: (
2547:minutes
2478:Bibcode
2441:Bibcode
2401:Bibcode
2356:Bibcode
2323:2390534
2303:Bibcode
2291:: A79.
1717:, p. 6.
1630:Bibcode
1569:2 April
1506: s
1425:⁄
1371:of the
1139:of the
1081:Canopus
804:Huygens
703:quasars
600:History
552: s
475:J1900.0
364:año luz
308:is the
277:in one
127:) units
2735:parsec
2519:
2374:
2321:
2024:
1994:
1957:
1931:
1858:
1832:
1755:
1622:Nature
1383:; see
1369:radius
1347:R136a1
1343:quasar
1339:3C 273
1265:, the
1202:3C 273
1190:R136a1
1137:centre
1022:Sirius
814:Saturn
724:Value
715:length
675:parsec
650:aether
642:Fizeau
456:parsec
310:parsec
220:
185:5.8786
153:
137:9.4607
121:metric
102:in ...
87:Symbol
82:length
2883:Light
2819:Stars
2755:(Gpc)
2749:(Mpc)
2743:(kpc)
2372:S2CID
2346:arXiv
2319:S2CID
2293:arXiv
2281:(PDF)
1711:" in
1485:Notes
837:Pluto
810:Titan
806:probe
727:Item
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